1. Field of the Invention
The present invention relates to an extreme ultra-violet (EUV) beam generation apparatus using multi-gas cell modules, and more particularly, to an EUV beam generation apparatus using multi-gas cell modules in which a gas is prevented from directly flowing into a vacuum chamber by adding an auxiliary gas cell serving as a buffer chamber to a main gas cell, a diffusion rate of the gas is decreased, a high vacuum state is maintained, and a higher power EUV beam is continuously generated.
2. Discussion of Related Art
Generally, an extreme ultra-violet (EUV) beam, for example, electromagnetic radiation (also known as soft X-rays) having a wavelength of about 50 nm or less, which includes light having a wavelength of 13.5 nm, can be used in a photolithography process to form a very small pitch on a substrate, for example, a silicon wafer.
That is, EUV light and X-rays are located in a shorter wavelength region than visible light, and thus can improve measurement resolution according to a diffraction limit which limits sizes of wavelengths in precision measurement using light, and can be used for fine measurement or nondestructive testing involved in biotechnology using a good transmission characteristic by extending to the X-ray region.
Specifically, when a good coherent light source can be generated at the same time, various applications using interference and diffraction phenomena of light are possible. Since a repetition rate of an incident femtosecond laser can be maintained, it can be used for precision spectroscopy, frequency standard measurement, or the like in EUV and X-ray regions.
One of the various methods of generating EUV light and X-rays is a method using a synchrotron. When EUV light and X-rays are generated using the synchrotron, there are advantages in that a large amount of light of good quality can be obtained and various wavelength bands can be obtained at the same time, however, since a facility itself is very enormous and expensive, there is a problem in that it cannot be simply configured in a laboratory stage.
Recently, as a method of overcoming this problem, a high-order harmonic generation (HHG) method using a femtosecond laser has been proposed, and thus coherent EUV light and soft X-rays can be generated with a relatively small experimental device.
In the HHG method, electrons are ionized, move along a track and are recombined by applying a high time-varying electric field to an inert gas such as, for example, argon (Ar), neon (Ne), xenon (Xe), and the like, and the energy corresponding to the sum of the ionization energy and kinetic energy of the electrons generates light of the EUV and X-ray band.
HHG has typically been designed or made so that an inert gas is injected into a gas cell and the used inert gas naturally leaves the gas cell.
However, in the conventional technique, the inert gas leaving the gas cell is immediately discharged into the vacuum chamber, and thus it is disadvantageous in that an environment in the vacuum chamber is contaminated or a degree of vacuum inside the vacuum chamber is decreased. Specifically, the generated EUV beam is absorbed by the inert gas exposed inside the vacuum chamber, and thus there is a serious problem in that the output of the EUV beam is reduced.
In order to address the above problem, in Korea Patent No. 10-1349898 (module for extreme ultra-violate beam generation) filed and registered by the same applicant, a module for generating a EUV beam which is a high-order harmonic by interacting a laser beam with an inert gas in a vacuum chamber is disclosed.
However, in the above related art, which is related to a single gas cell module, gas is injected in a vacuum state and a laser passes therethrough, and an EUV beam generated at this time should be measured. It is difficult to control an amount of the gas for maintaining a degree of vacuum due to the instantaneous diffusion of the gas injected inside the vacuum chamber as well as difficult to maintain a vacuum state due to the injected gas, and it is difficult to maintain the degree of vacuum. Thus, there is a problem in that the EUV beam cannot be continuously generated for a long time.